Biochemical conversion of Brassica carinata biomass to organic acids

The economics of the inedible oilseed crop Brassica carinata as a source of renewable fuels can be enhanced by converting its cellulosic biomass to value-added chemicals, such as organic acids. We investigated the biochemical conversion of carinata biomass to propionic acid by first pretreating the carinata meal (CM), which is obtained after extraction of the oil from carinata seeds, with concentrated phosphoric acid to remove hemicellulose and gain access to the cellulose constituent of the meal. We then subjected the pretreated meal to enzymatic hydrolysis with cellulase enzyme to depolymerize cellulose to glucose. The overall conversion of carinata cellulose to glucose was 85%, which is promising. Finally, the recovered glucose was successfully fermented primarily to propionic acid using the bacterium Propionibacterium freudenreichii with a yield of 0.57 g of produced propionic acid per gram of consumed cellulosic glucose. The biobased propionic acid and other co-produced organic acids can serve as renewable building blocks for manufacturing industrial chemicals and food preservatives replacing fossil-derived organic acids. Hence, CM constitutes a renewable source of fermentable carbohydrates potentially improving the economics and sustainability of the carinata value chain.

Automated summary

The study demonstrates that converting Brassica carinata cellulose into propionic acid has promising economic potential and sustainability. By enzymatic hydrolysis and fermentation of pretreated carinata meal (CM), propionic acid can be efficiently produced as a renewable raw material for industrial chemicals and food preservatives.